import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
    private DatagramSocket socket ;

    public UdpEchoServer(int port) throws SocketException {
        this.socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务启动");
        while (true){
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096] , 4096) ;
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData() , 0 , requestPacket.getLength());
            String response = process(request);
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes() ,response.getBytes().length ,
                      requestPacket.getSocketAddress());
            socket.send(responsePacket);
            System.out.printf("[%s,%d]request= %s , response=%s\n" ,requestPacket.getAddress().toString(),requestPacket.getPort() ,
                    request , response);
        }
    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090) ;
        server.start();
    }

}
